1. Field of the Invention
The present invention relates to a sheet feeding apparatus and an image forming apparatus, in particular, a sheet feeding apparatus and an image forming apparatus which separate sheets one by one by using a separation claw and feed the separated sheets.
2. Description of the Related Art
In recent years, an image forming apparatus such as a printer, a copying machine, and a facsimile includes a sheet feeding apparatus configured to separate sheets one by one and feeding each of the sheets to an image forming portion. As the above-mentioned sheet feeding apparatus, the following sheet feeding apparatus is known. Specifically, in the sheet feeding apparatus, a sheet containing portion includes a rising and lowering sheet supporting portion configured to support the sheets stacked thereon. The sheet supporting portion is raised up to a sheet feeding position at which the uppermost sheet of the sheets stacked on the sheet supporting portion can be fed by a feed roller. Then, the feed roller feeds the uppermost sheet.
Here, as a system of separating the sheets one by one during sheet feeding, there is known a system including separation claws configured to restrain, in a leading edge of the sheets stacked on the sheet supporting portion, both side edges in a width direction orthogonal to a sheet feeding direction of the sheets. In the separation system using separation claws, the separation claws deflect and then flick each of the sheets, which have been fed by the feed roller, so as to separate the sheets one by one. However, some types of sheets have stiffness or frictional coefficient different from each other. Therefore, timing when each of the sheets moves away from the separation claws and slipping state of the feed roller with respect to each of the sheets may be different among the sheets. In this case, feeding amount of the sheets may decrease or increase. In a case where the feeding amount of the sheets is small, the sheets cannot be separated by the separation claws. This leads to feeding failure. In a case where the feeding amount of the sheets is large, each of the sheets is incapable of climbing over the separation claws, and hence a corner(s) of each of the sheets is (are) bent. This causes damage to the sheets. With this regard, Japanese Patent Application Laid-Open No. H08-012115 discloses the following sheet feeding apparatus. Specifically, in the sheet feeding apparatus, depending on the type of sheet, positions of the separation claws and a position of the sheet supporting portion in the sheet feeding direction with respect to the feed roller are integrally changed. In this way, each of the sheets can be stably fed. Further, the above-mentioned configuration is capable of feeding even sheets such as label sheets having high frictional coefficient between the sheets and large stiffness.
However, in the above-mentioned conventional sheet feeding apparatus having the configuration of integrally changing the positions of the separation claws and the position of sheet supporting portion with respect to the feed roller, a mechanism configured to change the positions of the separation claws and the position of the sheet supporting portion is required. Further, in a case where the above-mentioned mechanism configured to change the positions is provided, it is possible to feed sheets having high frictional coefficient between the sheets and large stiffness. However, provision of the above-mentioned mechanism leads to an increase in cost and size of the sheet feeding apparatus. The increase in size of the sheet feeding apparatus occurs because space is required for moving the separation claws and the sheet supporting portion. Further, a user needs to change setting depending on the type of the sheets, and hence there is a problem of taking labor hour for setting.